Antenna device and communication device

ABSTRACT

An antenna device and a communication device capable of changing over polarization characteristics of an antenna to improve transmission capacity in various kinds of polarization environments and used configuration by preventing reduction of the communication capacity for a reception signal degrading or varying depending on momentarily changing polarization conditions between a base station and a terminal. The antenna device ( 110 ) includes a plurality of first antenna elements ( 111,112 ) for a first polarizing direction, a second antenna element ( 121 ) provided in the direction orthogonal to the first polarizing direction, a plurality of switches ( 131,132 ) for switching connection between the plurality of first antenna elements ( 111,112 ) and the second antenna element ( 121 ), and power supply parts ( 141,142 ) respectively provided on the plurality of first antenna elements ( 111,112 ).

TECHNICAL FIELD

The present invention relates to an antenna apparatus and communicationapparatus such as a mobile telephone device. In particular, the presentinvention relates to an antenna apparatus and communication apparatususing a plurality of antenna elements for performing diversityoperations, MIMO (Multiple-Input Multiple-Output) communication oradaptive array antenna operations.

BACKGROUND ART

An antenna apparatus is provided in various communication devices totransmit and receive radio waves of a predetermined frequency band. Thepopularity and the range of application of portable radio devicesrepresented by mobile telephones have grown, and therefore there is agrowing demand for wideband capability of portable radio deviceantennas. Also, with the rapid spread of portable radio devices, thenumber of channels in one wireless communication system is likely to beinsufficient. Consequently, studies are underway to use one systemtogether with other wireless communication systems using differentfrequency bands to secure a necessary number of channels. Withsignificant advances in techniques for reducing size and weight, as aterminal, a single portable radio device that can use two kinds ofwireless communication systems have been developed. Moreover, abandwidth of several hundreds MHz is considered to be necessary in theUHF band for, for example, reception of terrestrial digital broadcast.Furthermore, to reduce the size of a radio apparatus by supporting aplurality of WLAN (Wireless Local Area Network) standards usingdifferent frequency bands by means of a single antenna, for example, anantenna covering the 2.4 GHz and 5.2 GHz bands is required.

In communication between a mobile station and base station in a mobilecommunication system, fading often occurs in which the received signallevel fluctuates depending on various radio wave propagationenvironments. Effective measures to take against fading includeproviding antenna selective diversity and combined diversity. Withantenna selective diversity, a plurality of antennas are generallyinstalled, and communication is performed by selecting an antenna withgood conditions when the receiving state degrades due to fading. Forexample, there are antenna selective diversity apparatuses with a TDMA(Time Division Multiple Access) communication scheme in which the samefrequency is shared by a plurality of users by means of time division.

Also, in recent wireless communication systems, MIMO communication hasattracted attention as a technique to improve the efficiency oftransmission. In MIMO communication, a transmitting apparatus having aplurality of transmitting antennas simultaneously transmit streamscomprised of a plurality of bits from these transmitting antennas, and areceiving apparatus having a plurality of receiving antennas demultiplexand demodulate those streams from the transmitting apparatus. Therefore,when mutually different streams are simultaneously transmitted from allof the transmitting antennas of the transmitting apparatus, compared tothe case of one transmitting antenna, theoretically, it is possible toincrease the efficiency of transmission to the multiples of the numberof transmitting antennas.

In communication providing a plurality of antenna elements and adoptingdiversity operations, MIMO communication or adaptive array antennaoperations, the directivity of a single antenna alone is not sufficientto cope with the fluctuation of polarization conditions which changeevery minute between a base station and a terminal. In particular, thedirectivity of a single antenna alone is not sufficient to cope with thefluctuation of polarization characteristics of received signals. Tosecure the communication capacity, an antenna system is necessary whichflexibly responds to the fluctuation of polarization characteristics.

As measures to take against the above, Patent Documents 1 to 4 disclosetechniques to improve communication capacity utilizing polarization.

Patent Document 1 discloses a communication apparatus and method usingadaptive array antennas by which a base station switches polarizationcharacteristics and in which the terminal side performs reception with apolarization matching a polarization characteristic from the basestation. With the apparatus disclosed in Patent Document 1, if the basestation outputs a vertically polarized wave, the terminal receives thiswith vertical polarization. By this means, antenna polarization matchesbetween the terminal and the base station, so that it is possible toimprove communication capacity. Further, by performing communicationusing polarizations which change between terminals, it is possible tosuppress the interference for communication paths between the terminalsand the base station.

Patent Document 2 discloses a radio wave transmitting and receivingapparatus for improving communication capacity by providing a pluralityof antenna elements of different polarizations in a base station,implementing selective diversity and performing MIMO operations usingthis antenna group.

Patent Document 3 discloses an antenna apparatus that performsdirectivity synthesis using a plurality of antenna elements from a largenumber of antenna elements and then performs MIMO communication.

Patent Document 4 discloses a MIMO wireless communication system forproviding a plurality of antenna elements of different polarizationsboth in a base station and in a terminal, and performing MIMO. By thismeans, the directivity and polarization change between antenna elementsfor transmission and reception in MIMO propagation paths, and theseparation level between propagation paths improves, so that it ispossible to improve communication capacity.

-   Patent Document 1: Japanese Patent Application Laid-Open Number    2004-80353-   Patent Document 2: Japanese Patent Application Laid-Open Number    2004-312381-   Patent Document 3: Japanese Patent Application Laid-Open Number    2005-86518-   Patent Document 4: Japanese Patent Application Laid-Open Number    2004-517549

DISCLOSURE OF INVENTION Problems to be Solved by the Invention

However, such a conventional portable radio device having a plurality ofantenna elements has the following problems.

(1) In the apparatus disclosed in Patent Document 1, a base stationcommunicates with terminals by switching polarization characteristicsper antenna and the apparatus switches polarization from the basestation per terminal, thereby improving separation between communicationpaths. However, with this technique, polarization from a base stationchanges depending on the propagation environment, and, consequently, itis difficult to secure the separation level between paths in terminals.Also, polarization of terminals is not fixed in mobile telephones, andtherefore it is difficult to separate paths.

(2) The apparatus disclosed in Patent Document 2 selects the bestantenna element from an antenna group having a plurality of antennaelements of different polarizations and implement diversity or performMIMO using that antenna element. However, with this technique, althoughthe transmission capacity in MIMO is increased by switching polarizationper antenna, the gradient of terminals is not taken into account, andtherefore the transmission capacity may be degraded depending on thecondition of gradient.

(3) The apparatus disclosed in Patent Document 3 performs directivitysynthesis using a plurality of antenna elements from a large number ofantenna elements and then performs MIMO communication. That is, byperforming directivity synthesis after adjusting the amplitude and phaseusing a plurality of antenna elements, it is possible to providedirectivity suitable to various propagation characteristics andpolarization characteristics. However, this technique does not disclosethat the terminal side acquires an antenna of an optimal polarizationcharacteristic not depending on the operating states of a base station,propagation environment and terminal. Further, this technique does notdisclose an antenna apparatus that provides various polarizationpatterns in accordance with polarization characteristics, where thesepolarization characteristics provide extremely low power loss and changedepending on place and time.

(4) The apparatus disclosed in Patent Document 4 provides a plurality ofantenna elements of different polarizations both in a base station andin a terminal, and performs MIMO. The polarizations of antennas are notswitched depending on changes in the propagation environment, and thesame directivities and polarization characteristics are always used.Similar to the apparatus disclosed in Patent Document 3, this techniquedoes not disclose that the terminal side acquires an antenna of anoptimal polarization characteristic not depending on the operatingstates of a base station, propagation environment and terminal. Further,this technique does not disclose an antenna apparatus that providesvarious polarization patterns in accordance with polarizationcharacteristics, where these polarization characteristics provideextremely low power loss and change depending on place and time

Therefore, with an antenna apparatus and communication apparatus using aplurality of conventional antenna elements, when a base station andterminal perform communication, it is necessary to provide a largercommunication capacity more reliably by responding to changes inpolarization by antennas. Here, changes in polarization occur dependingon: polarizations of base station antennas; changes in polarizationcharacteristics due to radio propagation characteristics between thebase station and the terminal; the method of using the terminal by theuser; and various conditions such as the gradient of the terminal.

In view of the above, it is an object of the present invention toprovide an antenna apparatus and communication apparatus that can switchantenna polarization characteristics, prevent the decrease incommunication capacity for received signals that attenuate or fluctuatedepending on the conditions of polarization that changes every minutebetween a base station and a terminal.

Means for Solving the Problem

The antenna apparatus of the present invention employs a configurationhaving: at least two first antenna elements for a first polarizationdirection; a second antenna element that is set in a directionorthogonal to the first polarization direction; a switch that switchesconnections between the first antenna elements and the second antennaelement; and a feeding section that is set in each of the first antennaelements.

The communication apparatus of the present invention employs aconfiguration having the above antenna apparatus used for MIMO (MultipleInput Multiple Output) or diversity.

Advantageous Effect Of The Invention

According to the present invention, by switching the antennapolarization characteristics, it is possible to provide optimal antennaperformance for received signals that attenuate or fluctuate dependingon the conditions of polarization that changes every minute between abase station and a terminal. Further, it is equally possible to providean advantage of preventing the decrease in communication capacity incommunication using a plurality of antenna elements for performingdiversity operations, MIMO communication or adaptive array antennaoperations. By this means, for example, it is possible to flexibly copewith changes in polarization that occur depending on: polarizationcharacteristics of base station antennas; radio propagationcharacteristics between the base station and a terminal; the method ofusing the terminal by the user; and various conditions such as thegradient of the terminal. Therefore, it is possible to provide the bestsignal level, prevent the decrease in communication capacity and improvetransmission capacity in various polarization environments and usagetypes.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 shows an outline configuration of a portable radio devicemounting an antenna apparatus according to Embodiment 1 of the presentinvention;

FIG. 2 shows an outline configuration of a portable radio devicemounting the above antenna apparatus according to Embodiment 1;

FIG. 3A illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 1;

FIG. 3B illustrates switching polarization characteristics of the aboveantenna apparatus according to Embodiment 1;

FIG. 3C illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 1;

FIG. 4 shows a table illustrating switching of polarizationcharacteristics in FIGS. 3A to 3C;

FIG. 5 shows an outline configuration of a portable radio devicemounting an antenna apparatus according to Embodiment 2 of the presentinvention;

FIG. 6A illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 2;

FIG. 6B illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 2;

FIG. 6C illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 2;

FIG. 7 shows a table illustrating switching of polarizationcharacteristics in FIGS. 6A to 6C;

FIG. 8 shows an outline configuration of a portable radio devicemounting an antenna apparatus using a plurality of antenna elementsaccording to Embodiment 3 of the present invention;

FIG. 9A shows a perspective view of an outline configuration of aportable radio device mounting the above antenna apparatus according toEmbodiment 3;

FIG. 9B shows a perspective view of an outline configuration of aportable radio device mounting the above antenna apparatus according toEmbodiment 3;

FIG. 10A illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10B illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10C illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10D illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10E illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10F illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10G illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10H illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 10I illustrates switching of polarization characteristics of theabove antenna apparatus according to Embodiment 3;

FIG. 11 shows a table illustrating switching of polarizationcharacteristics in FIGS. 10A to 10C;

FIG. 12 shows a table illustrating switching of polarizationcharacteristics in FIGS. 10D to 10F;

FIG. 13 shows a table illustrating switching of polarizationcharacteristics in FIGS. 10G to 10I;

FIG. 14 illustrates a method of directly connecting feeding points ofthe above antenna apparatus according to Embodiment 3;

FIG. 15A shows a perspective view of an outline configuration of aportable radio device mounting the above antenna apparatus using aplurality of antenna elements according to Embodiment 4 of the presentinvention;

FIG. 15B shows a perspective view of an outline configuration of aportable radio device mounting the above antenna apparatus using aplurality of antenna elements according to Embodiment 4; and

FIG. 16 shows a perspective view of an outline configuration of aportable radio device mounting an antenna apparatus using a plurality ofantenna elements according to Embodiment 5 of the present invention

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be explained below in detailwith reference to the accompanying drawings.

(Embodiment 1)

FIG. 1 shows an outline configuration of a portable radio devicemounting an antenna apparatus using a plurality of antenna elementsaccording to Embodiment 1 of the present invention. An example case willbe described where the present embodiment is applied to a portable radiodevice mounting a terminal antenna apparatus used in MIMO communicationor diversity communication.

In FIG. 1, portable radio device 100 has, inside the housing, antennaapparatus 110 using a plurality of antenna elements used in MIMOcommunication or diversity communication.

Portable radio device 100 only needs to represent a portable radiodevice mounting antenna apparatus 110 using a plurality of antennaelements used in MIMO communication or diversity communication, such asa mobile telephone device and PHS (Personal Handy-phone System). Also,portable information terminals such as PDA's (Personal DigitalAssistants) and information processing apparatuses such as a laptopcomputer are applicable.

The housing of portable radio device 100 is formed with a moldedinsulating resin such as a non-conductive ABS resin. Also, as measuresto take against degradation in antenna efficiency upon close antennaelements, for example, the housing uses metamaterials to preventdegradation in antenna efficiency. Also, as is not shown in the figure,portable radio device 100 is provided with an LCD display section, asubscreen display section, a speaker that outputs, for example, aringtone, a camera section that photographs an image, a connector thatconnects with external devices, and so on.

Antenna apparatus 110 is provided with first antenna elements 111 and112 for the first polarization direction, second antenna element 121that is set in the direction orthogonal to the first polarizationdirection, switches 131 and 132 that switch connection between firstantenna elements 111 and 112 and second antenna element 121, and feedingsections 141 and 142 that are provided in first antenna elements 111 and112, respectively.

As shown in FIG. 1, antenna apparatus 110 employs a configuration inwhich three antenna elements (i.e. first antenna elements 111 and 112and second antenna element 121) are arranged in the shape of the letter“U,” two switches (i.e. switches 131 and 132) are arranged between theseantenna elements, and two feeding sections (i.e. feeding sections 141and 142) are arranged in one end of first antenna elements 111 and 112.

Assume that first antenna elements 111 and 112 and second antennaelement 121 are formed with metal frames and have a length ofapproximately λ/4 (where λ is the wavelength) in the longitudinaldirection. Regarding the antenna element parallel to the housing, whenthis antenna element is set as far as possible from this housing, theantenna efficiency improves and is therefore advantageous. The materialsnaturally carries radio waves, and examples include copper, iron andmagnesium alloy providing a high conduction level with low loss at usedfrequencies and having high hardness with lightweight.

Switches 131 and 132 switch the connections between second antennaelement 121 and first antenna element 111 and/or first antenna element112, according to a control signal from a control section (not shown).Also, the control section (not shown) outputs a control signal toswitches 131 and 132 for switching the connections according to thepolarization direction.

Switches 131 and 132 use switches providing minimum loss at usedfrequencies in the case where switches 131 and 132 are turned on, anduse switches providing as much isolation as possible in the case whereswitches 131 and 132 are turned off. Further, switches 131 and 132 needto withstand the large power of transmission waves upon transmission.For example, it is preferable to use MEMS (Micro-Electro-MechanicalSystem) switches with low loss. Also, specific examples of combinationsof switching in switches 131 and 132 will be described later.

Feeding sections 141 and 142 are formed with conductive metals andconnected with first antenna elements 111 and 112 for feeding theseantenna elements.

If switch 131 is turned off and first antenna element 111 and secondantenna element 121 are separated from each other, first antenna element111 and feeding section 141 operate as a monopole antenna. Similarly, ifswitch 132 is turned off and first antenna element 112 and secondantenna element 121 are separated from each other, first antenna element112 and feeding section 142 operate as an monopole antenna. Also, secondantenna element 121 is arranged orthogonal to first antenna elements 111and 112 such that second antenna element 121 links these two monopolefeeding sections.

Here, antenna apparatus 110 incorporated in portable radio device 100may be mounted transversely to the housing of portable radio device 100.

FIG. 2 shows an outline configuration of portable radio device 100having above antenna apparatus 110. The same components as in FIG. 1will be assigned the same reference numerals.

As shown in FIG. 2, three antenna elements are arranged in the shape ofthe letter “U” such that antenna apparatus 110 is transversely arrangedto the housing of portable radio device 100. If antenna apparatus 110 istransversely arranged, the performance is the same as in FIG. 1. Byarranging antenna apparatus 110 transversely, it is possible to improvethe degree of freedom of arrangement of parts in the housing.

The operations of antenna apparatus 110 configured as above will beexplained.

An example case will be described where MIMO communication that switchespolarization characteristics depending on the condition is performed tocope with various polarizations.

FIGS. 3A to 3C illustrate switching of polarization characteristics ofantenna apparatus 110, where FIG. 3A shows vertical polarization inMIMO, FIG. 3B shows diagonal polarization (MIMO+) and FIG. 3C showsdiagonal polarization (MIMO−). Also, FIG. 4 shows a table illustratingswitching of polarization characteristics in FIGS. 3A to 3C. In FIGS. 3Ato 3C and FIG. 4, diagonal polarization is inclined at +45 degrees or−45 degrees from vertical polarization. The direction of polarization isshown by the arrow points in the figure. SW 1 and SW 2 representswitches 131 and 132, and Rx 1 and Rx 2 represent the receiving ends ofportable radio device 100 with which antenna apparatus 110 is connected.Also, V represents vertical polarization. Also, if this antennaapparatus 110 is applied to the base station side that performs MIMOcommunication, Rx 1 and Rx 2 need to be read as Tx 1 and Tx 2.

[First Scheme (Mode 1)]

As shown in FIG. 3A and FIG. 4, switch 131 (SW 1) and switch 132 (SW 2)are turned off. Then, second antenna element 121 is separated from firstantenna elements 111 and 112, and only first antenna elements 111 and112 in the first polarization direction perform monopole antennaoperations. Therefore, antenna apparatus 110 has antenna characteristicsof (90 degrees-90 degrees) polarization.

[Second Scheme (Mode 2)]

As shown in FIG. 3B and FIG. 4, switch 131 (SW 1) is turned on andswitch 132 (SW 2) is turned off. Then, first antenna element 111 andsecond antenna element 121 are connected, and second antenna element 121and first antenna element 112 are separated. Second antenna element 121is arranged in the direction orthogonal to first antenna element 111,and, consequently, when first antenna element 111 and second antennaelement 121 are connected, the antenna element formed with first antennaelement 111 and second antenna element 121 provides diagonalpolarization inclined at +45 degrees from vertical polarization. Firstantenna element 112 in the first polarization direction performsmonopole antenna operations. Therefore, antenna apparatus 110 hasantenna characteristics of (+45 degrees-90 degrees) polarization.

[Third Scheme (Mode 3)]

As shown in FIG. 3C and FIG. 4, switch 131 (SW 1) is turned off andswitch 132 (SW 2) is turned on. Then, first antenna element 112 andsecond antenna element 121 are connected, and second antenna element 121and first antenna element 111 are separated. Similar to first antennaelement 111, second antenna element 121 is arranged in the directionorthogonal to first antenna element 112, and, consequently, when firstantenna element 112 and second antenna element 121 are connected, theantenna element formed with first antenna element 112 and second antennaelement 121 provides diagonal polarization inclined at −45 degrees fromvertical polarization. First antenna element 111 in the firstpolarization direction performs monopole antenna operations. Therefore,antenna apparatus 110 has antenna characteristics of (90 degrees-(−45)degrees) polarization.

As shown in the table of FIG. 4, by switching switch 131 (SW 1) andswitch 132 (SW 2), antenna apparatus 110 can provide three types ofantenna characteristics of (90 degrees-90 degrees) polarization, (45degrees-90 degrees) polarization and (90 degrees-(−45) degrees)polarization. By this means, even in the case where mismatch ofpolarization occurs in a receiving antenna due to the antennaconfiguration of the base station, the rotation of propagatingpolarization and the gradient of the terminal (e.g. portable radiodevice 100), it is possible to improve the receiving level by threevariations of antenna polarizations. In particular, these antennapolarizations are effective to improve the received signal level in MIMOand diversity communication.

As described above, according to the present embodiment, antennaapparatus 110 is provided with first antenna elements 111 and 112 forthe first polarization direction, second antenna element 121 set in thedirection orthogonal to the first polarization direction, switches 131and 132 that switch the connections between first antenna elements 111and 112 and second antenna element 121, and feeding sections 141 and 142provided in first antenna elements 111 and 112, respectively. Byswitching switches 131 and 132 and changing operating antenna elements,it is possible to switch the polarization characteristics of antennaapparatus 110, so that it is possible to provide antenna performance tocope with the condition of polarization that changes every minutebetween a base station and a terminal. By this means, it is possible toimprove transmission capacity in various polarization environments andusage types. For example, in the case of portable radio device 100mounting antenna apparatus 110 shown in FIG. 1, in MIMO communication ordiversity communication, even if polarization of a base stationfluctuates, propagating polarization fluctuates or polarizationfluctuates due to various causes such as polarization changes caused bythe gradient of the terminal, it is possible to perform MIMOcommunication or diversity communication with high transmission capacityby controlling switches 131 and 132 mounted on antenna apparatus 110 andproviding the antenna directivity of optimal polarizationcharacteristics according to the operation state.

Also, with the present embodiment, by using MEMS switches of low loss asswitches 131 and 132, it is possible to alleviate the power loss due toswitching and prevent the decrease in communication capacity.

(Embodiment 2)

FIG. 5 shows an outline configuration of a portable radio devicemounting an antenna apparatus using a plurality of antenna elementsaccording to Embodiment 2 of the present invention. In the explanationof the present embodiment, the same components as in FIG. 1 will beassigned the same reference numerals and overlapping explanation will beomitted.

In FIG. 5, portable radio device 200 has built-in antenna apparatus 210using a plurality of antenna elements used in MIMO communication ordiversity communication.

Antenna apparatus 210 is provided with first antenna elements 111 and112 for the first polarization direction, second antenna element 121 setin the direction orthogonal to the first polarization direction,switches 131 and 132 that are set at one end of first antenna elements111 and 112 and that switch the connections between first antennaelements 111 and 112 and second antenna element 121, and feedingsections 141 and 142 that are set in the other end of first antennaelements 111 and 112, respectively.

Antenna apparatus 210 differs from FIG. 1 only in arranging secondantenna element 121 and switches 131 and 132 on the side opposite to theside of feeding sections 141 and 142 of antenna elements 111 and 112.Therefore, similar to antenna apparatus 110 in FIG. 1, antenna apparatus210 employs a configuration where three antenna elements (i.e. firstantenna elements 111 and 112 and second antenna element 121) arearranged in the shape of the letter “U,”, two switches (i.e. switches131 and 132) are arranged between these antenna elements, and twofeeding sections (i.e. feeding sections 141 and 142) are arranged in oneend of first antenna elements 111 and 112.

Here, as is not shown in the figure, antenna apparatus 210 incorporatedin portable radio device 100 may be provided transversely to the housingof portable radio device 200.

The operations of antenna apparatus 210 configured as above will beexplained below.

The basic operations are the same as in Embodiment 1. An example casewill be described where MIMO communication that switches polarizationcharacteristics depending on the condition is performed.

FIGS. 6A to 6C illustrate switching of polarization characteristics ofantenna apparatus 210, where FIG. 6A shows vertical polarization inMIMO, FIG. 6B shows diagonal polarization (MIMO−) and FIG. 6C showsdiagonal polarization (MIMO+). Also, FIG. 7 shows a table illustratingswitching of polarization characteristics in FIGS. 6A to 6C. In FIGS. 6Ato 6C and FIG. 7, diagonal polarization is inclined at +45 degrees or−45 degrees from vertical polarization. SW 1 and SW 2 represent switches131 and 132, and Rx 1 and Rx 2 represent the receiving ends of portableradio device 200 with which antenna apparatus 210 is connected. Also, Vrepresents vertical polarization. Also, if this antenna apparatus 210 isapplied to the base station side that performs MIMO communication, Rx 1and Rx 2 need to be read as Tx 1 and Tx 2.

[Fourth Scheme (Mode 4)]

As shown in FIG. 6A and FIG. 7, switch 131 (SW 1) and switch 132 (SW 2)are turned off. Then, second antenna element 121 is separated from firstantenna elements 111 and 112, and only first antenna elements 111 and112 in the first polarization direction perform monopole antennaoperations. Therefore, antenna apparatus 210 has antenna characteristicsof (90 degrees-90 degrees) polarization.

[Fifth Scheme (Mode 5)]

As shown in FIG. 6B and FIG. 7, switch 131 (SW 1) is turned on andswitch 132 (SW 2) is turned off. Then, first antenna element 111 andsecond antenna element 121 are connected, and second antenna element 121and first antenna element 112 are separated. Second antenna element 121is arranged in the direction orthogonal to first antenna element 111,and, consequently, when first antenna element 111 and second antennaelement 121 are connected, the antenna element formed with first antennaelement 111 and second antenna element 121 provides diagonalpolarization inclined at +45 degrees from vertical polarization. Firstantenna element 112 in the first polarization direction performsmonopole antenna operations. Therefore, antenna apparatus 210 hasantenna characteristics of (−45 degrees-90 degrees) polarization.

[Sixth Scheme (Mode 6)]

As shown in FIG. 6C and FIG. 7, switch 131 (SW 1) is turned off andswitch 132 (SW 2) is turned on. Then, first antenna element 112 andsecond antenna element 121 are connected, and second antenna element 121and first antenna element 111 are separated. Similar to first antennaelement 111, second antenna element 121 is arranged in the directionorthogonal to first antenna element 112, and, consequently, when firstantenna element 112 and second antenna element 121 are connected, theantenna element formed with first antenna element 112 and second antennaelement 121 provides diagonal polarization inclined at −45 degrees fromvertical polarization. First antenna element 111 in the firstpolarization direction performs monopole antenna operations. Therefore,antenna apparatus 210 has antenna characteristics of (90 degrees-45degrees) polarization.

As shown in the table of FIG. 7, by switching switch 131 (SW 1) andswitch 132 (SW 2), antenna apparatus 210 can provide three types ofantenna characteristics of (90 degrees-90 degrees) polarization, (−45degrees-90 degrees) polarization and (90 degrees-45 degrees)polarization. By this means, even in the case where mismatch ofpolarization occurs in a receiving antenna due to the antennaconfiguration of the base station, the rotation of propagatingpolarization and the gradient of the terminal (e.g. portable radiodevice 200), it is possible to improve the receiving level by threevariations of antenna polarizations. In particular, these antennapolarizations are effective to improve the received signal level in MIMOand diversity communication. By switching switches 131 and 132 andchanging operating antenna elements, it is possible to switch thepolarization characteristics of antenna apparatus 210, so that it ispossible to provide antenna performance to cope with the condition ofpolarization that changes every minute between a base station and aterminal. By this means, it is possible to improve transmission capacityin various polarization environments and usage types.

(Embodiment 3)

Cases have been described with Embodiments 1 and 2 where an antennaapparatus uses a plurality of antenna elements used in 2×2 MIMOcommunication or diversity communication. A case will be explained withEmbodiment 3 where an antenna apparatus uses a plurality of antennaelements used in 3×3 MIMO communication or diversity communication.

FIG. 8 shows an outline configuration of a portable radio devicemounting an antenna apparatus using a plurality of antenna elementsaccording to Embodiment 3 of the present invention. In the explanationof the present embodiment, the same components as in FIG. 1 will beassigned the same reference numerals and overlapping explanation will beomitted.

In FIG. 8, portable radio device 300 has built-in antenna apparatus 310using a plurality of antenna elements used in MIMO communication ordiversity communication.

Antenna apparatus 310 is provided with first antenna elements 111, 112and 113 for the first polarization direction, second antenna elements121 and 122 set in the direction orthogonal to the first polarizationdirection, switches 131, 132, 133 and 134 that switch the connectionsbetween first antenna elements 111, 112 and 113 and second antennaelements 121 and 122, and feeding sections 141, 142 and 143 that are setin first antenna elements 111, 112 and 113.

Antenna apparatus 310 employs a configuration adding first antennaelement 113, second antenna element 122, switches 133 and 134 andfeeding section 143 to antenna apparatus 110 in FIG. 1.

The present embodiment shows a configuration example of an antennaapparatus in 3×3 MIMO communication. The number of antenna elements, thenumber of switches and the number of feeding points in the antennaapparatus are generally shown as follows.

In the case of N×N MIMO (where N is an arbitrary natural number), thenumber of feeding points is N, the number of elements is N+(N−1) and thenumber of switches is (N−1)×2.

Here, as is not shown in the figure, antenna apparatus 310 incorporatedin portable radio device 300 may be provided transversely to the housingof portable radio device 300.

Also, although an example case has been described with FIG. 8 whereantenna apparatus 310 is incorporated in the housing of portable radiodevice 300, it is equally possible to set antenna apparatus 310 in anypositions such as the outside of portable radio device 300.

FIGS. 9A and 9B show a perspective view of an outline configuration of aportable radio device mounting above antenna apparatus 310. As shown inFIG. 9A, it is possible to arrange antenna apparatus 310 in the upperpart of portable radio device 300A, or cover antenna apparatus 310 withcover 320 as shown in FIG. 9B.

The operations of antenna apparatus 31 configured as above will beexplained.

The basic operations are the same as in Embodiment 1. An example casewill be described where 3×3 MIMO communication that switchespolarization characteristics depending on the condition is performed.

FIGS. 10A to 10I illustrate switching of polarization characteristics ofantenna apparatus 310, where FIGS. 10A and 10B show verticalpolarization in MIMO and FIGS. 10C to 10I show at least one diagonalpolarization in the receiving end of portable radio device 300. Also,FIGS. 11 to 13 show a table illustrating switching of polarizationcharacteristics in FIGS. 10A to 10I. In FIGS. 10A to 10I and FIGS. 11 to13, diagonal polarization is inclined at +45 degrees or −45 degrees fromvertical polarization. SW 1, SW 2 and SW 3 represent switches 131, 132and 133, and Rx 1, Rx 2 and Rx 3 represent the receiving end of portableradio device 310 with which antenna apparatus 300 is connected. Also, ifthis antenna apparatus 310 is applied to the base station side thatperforms MIMO communication, Rx 1, Rx2 and Rx 3 need to be read as Tx 1,Tx 2 and Tx 3.

[First Scheme (Model 1)]

As shown in FIG. 10A and FIG. 11, switch 131 (SW 1) to switch 134 (SW 4)are turned off. Then, second antenna elements 121 and 122 are separatedfrom first antenna elements 111, 112 and 113, and only first antennaelements 111, 112 and 113 in the first polarization direction performmonopole antenna operations. Therefore, antenna apparatus 310 hasantenna characteristics of (90 degrees-90 degrees-90 degrees)polarization.

[Second Scheme (Mode 2)]

As shown in FIG. 10B and FIG. 11, switches 131 (SW 1) and 134 (SW 4) areturned off and switches 132 (SW 2) and 133 (SW 3) are turned on. Then,first antenna element 112 and second antenna elements 121 and 122 areconnected, second antenna element 121 and first antenna element 111 areseparated, and second antenna element 122 and first antenna element 113are separated. Although second antenna elements 121 and 122 are arrangedin the direction orthogonal to first antenna elements 111, 112 and 113,second antenna elements 121 and 122 are connected equally on the sidesof first antenna element 112, and therefore the antenna element formedwith first antenna element 112 and second antenna elements 121 and 122provide vertical polarization. First antenna elements 111, 112 and 113in the first polarization direction perform monopole antenna operations.Therefore, antenna apparatus 310 has antenna characteristics of (90degrees-90 degrees-90 degrees) polarization.

[Third Scheme (Mode 3)]

As shown in FIG. 10C and FIG. 11, switch 131 (SW 1) is turned on, switch132 (SW 2) is turned off, switch 133 (SW 3) is turned off and switch 134(SW 4) is turned on. Then, first antenna element 111 and second antennaelements 121 are connected, first antenna element 113 and second antennaelement 122 are connected, and first antenna element 112 and secondantenna elements 121 and 122 are separated. Second antenna elements 121and 122 are arranged in the direction orthogonal to first antennaelements 111, 112 and 113, and, consequently, when first antenna element111 and second antenna element 121 are connected, the antenna elementformed with first antenna element 111 and second antenna element 121provides diagonal polarization inclined at +45 degrees from verticalpolarization. Similarly, when first antenna element 113 and secondantenna element 122 are connected, the antenna element formed with firstantenna element 113 and second antenna element 122 provides diagonalpolarization inclined at −45 degrees from vertical polarization. Firstantenna element 112 in the first polarization direction performsmonopole antenna operations. Therefore, antenna apparatus 310 hasantenna characteristics of (45 degrees-90 degrees-(−45) degrees)polarization.

[Fourth Scheme (mode 4)]

As shown in FIG. 10D and FIG. 12, switch 131 (SW 1) is turned off,switch 132 (SW 2) is turned off, switch 133 (SW 3) is turned on andswitch 134 (SW 4) is turned off. Then, first antenna element 112 andsecond antenna elements 122 are connected, second antenna element 121and first antenna element 111 are separated, and second antenna element122 and first antenna elements 113 are separated. Second antennaelements 122 is arranged in the direction orthogonal to first antennaelements 111, 112 and 113, and, consequently, when first antenna element112 and second antenna element 122 are connected, the antenna elementformed with first antenna element 112 and second antenna element 122provides diagonal polarization inclined at +45 degrees from verticalpolarization. First antenna elements 112 and 113 in the firstpolarization direction perform monopole antenna operations. Therefore,antenna apparatus 310 has antenna characteristics of (90 degrees-45degrees-90 degrees) polarization.

[Fifth Scheme (Mode 5)]

As shown in FIG. 10E and FIG. 12, switch 131 (SW 1) is turned off,switch 132 (SW 2) is turned off, switch 133 (SW 3) is turned off andswitch 134 (SW 4) is turned on. Then, first antenna element 113 andsecond antenna element 122 are connected, second antenna element 121 andfirst antenna element 111 are separated, and second antenna element 122and first antenna element 112 are separated. Second antenna elements 122is arranged in the direction orthogonal to first antenna elements 111,112 and 113, and, consequently, when first antenna element 113 andsecond antenna element 122 are connected, the antenna element formedwith first antenna element 113 and second antenna element 122 providesdiagonal polarization inclined at −45 degrees from verticalpolarization. First antenna elements 111 and 112 in the firstpolarization direction perform monopole antenna operations. Therefore,antenna apparatus 310 has antenna characteristics of (90 degrees-90degrees-(−45) degrees) polarization.

[Sixth Scheme (Mode 6)]

As shown in FIG. 10F and FIG. 12, switch 131 (SW 1) is turned off,switch 132 (SW 2) is turned on, switch 133 (SW 3) is turned off andswitch 134 (SW 4) is turned on. Then, first antenna element 112 andsecond antenna element 121 are connected, first antenna element 113 andsecond antenna element 122 are separated, second antenna element 121 andfirst antenna element 111 are separated, and second antenna element 122and first antenna element 112 are separated. Second antenna elements 121and 122 are arranged in the direction orthogonal to first antennaelements 111, 112 and 113, and, consequently, when first antenna element112 and second antenna element 121 are connected, the antenna elementformed with first antenna element 112 and second antenna element 121provides diagonal polarization inclined at −45 degrees from verticalpolarization. Similarly, when first antenna element 113 and secondantenna element 122 are connected, the antenna element formed with firstantenna element 113 and second antenna element 122 also providesdiagonal polarization inclined at −45 degrees from verticalpolarization. First antenna element 111 in the first polarizationdirection performs monopole antenna operations. Therefore, antennaapparatus 310 has antenna characteristics of (90 degrees-(−45)degrees-(−45) degrees) polarization.

[Seventh Scheme (Mode 7)]

As shown in FIG. 10G and FIG. 13, switch 131 (SW 1) is turned off,switch 132 (SW 2) is turned on, switch 133 (SW 3) is turned off andswitch 134 (SW 4) is turned off. Then, first antenna element 112 andsecond antenna element 121 are connected, second antenna element 122 andfirst antenna elements 112 and 113 are separated. Second antennaelements 121 is arranged in the direction orthogonal to first antennaelements 111, 112 and 113, and, consequently, when first antenna element112 and second antenna element 121 are connected, the antenna elementformed with first antenna element 112 and second antenna element 121provides diagonal polarization inclined at −45 degrees from verticalpolarization. First antenna elements 111 and 113 in the firstpolarization direction perform monopole antenna operations. Therefore,antenna apparatus 310 has antenna characteristics of (90 degrees-(−45)degrees-90 degrees) polarization.

[Eighth Scheme (Mode 8)]

As shown in FIG. 10H and FIG. 13, switch 131 (SW 1) is turned on, switch132 (SW 2) is turned off, switch 133 (SW 3) is turned off and switch 134(SW 4) is turned off. Then, first antenna element 111 and second antennaelements 121 are connected, second antenna element 122 and first antennaelements 112 and 113 are separated. Second antenna elements 121 isarranged in the direction orthogonal to first antenna elements 111, 112and 113, and, consequently, when first antenna element 111 and secondantenna element 121 are connected, the antenna element formed with firstantenna element 111 and second antenna element 121 provides diagonalpolarization inclined at +45 degrees from vertical polarization. Firstantenna elements 112 and 113 in the first polarization direction performmonopole antenna operations. Therefore, antenna apparatus 310 hasantenna characteristics of (45 degrees-90 degrees-90 degrees)polarization.

[Ninth Scheme (Mode 9)]

As shown in FIG. 10I and FIG. 13, switch 131 (SW 1) is turned on, switch132 (SW 2) is turned off, switch 133 (SW 3) is turned on and switch 134(SW 4) is turned off. Then, first antenna element 111 and second antennaelement 121 are connected, first antenna element 112 and second antennaelement 122 are connected, and second antenna element 122 and firstantenna element 113 are separated. Second antenna elements 121 and 122are arranged in the direction orthogonal to first antenna elements 111,112 and 113, and, consequently, when first antenna element 111 andsecond antenna element 121 are connected and first antenna element 112and second antenna element 122 are connected, the antenna element formedwith first antenna element 111 and second antenna element 121 and theantenna element formed with first antenna element 112 and second antennaelement 122 provide diagonal polarization inclined at +45 degrees fromvertical polarization. First antenna element 113 in the firstpolarization direction performs monopole antenna operations. Therefore,antenna apparatus 310 has antenna characteristics of (45 degrees-45degrees-90 degrees) polarization.

Thus, by switching switches 131 to 134 (SW 1 to SW 4), antenna apparatus310 can provide antenna characteristics of combinations of polarizationsin the tables shown in FIG. 12 and FIG. 13. By this means, even in thecase where mismatch of polarization occurs in a receiving antenna due tothe antenna configuration of the base station, the rotation ofpropagating polarization and the gradient of the terminal (e.g. portableradio device 300), it is possible to improve the receiving level byvarious variations of antenna polarizations. In particular, theseantenna polarizations are effective to improve the received signal levelin MIMO and diversity communication. That is, by switching betweenswitches 131 to 134 (SW 1 to SW 4) and changing operating antennaelements, it is possible to switch polarization characteristics withmore variations than in Embodiments 1 and 2, so that it is possible toprovide antenna performance to cope with the condition of polarizationthat changes every minute between a base station and a terminal. As aresult, it is possible to improve transmission capacity in variouspolarization environments and usage types.

Here, it is possible to use above antenna apparatus 310 of the sameconfiguration between the receiving side and the transmitting side. Asupplemental case will be explained where feeding points of antennaapparatus 310 are connected directly.

FIG. 14 illustrates a method of directly connecting feeding points ofantenna apparatus 310.

In the case of using antenna apparatus 310 on the receiving side, thereis no problem if feeding points of antenna apparatus 310 are directlyconnected. However, in the case of using antenna apparatus 310 in, forexample, a base station on the transmitting side, it is not possible todirectly connect feeding points of antenna apparatus 310. For example,in the case of using antenna apparatus 310 on the transmitting side, itis not possible to implement a combination of switch operations in whichswitch 131 (SW 1) and switch 132 (SW 2) are turned on or switch 133 (SW3) and switch 134 (SW 4) are turned on in FIG. 14.

(Embodiment 4)

FIG. 15 shows a perspective view of an outline configuration of aportable radio device mounting an antenna apparatus using a plurality ofantenna elements, according to Embodiment 4 of the present invention. Inthe explanation of the present embodiment, the same components as inFIG. 1 and FIG. 8 will be assigned the same reference numerals andoverlapping explanation will be omitted.

In FIGS. 15A and 15B, antenna apparatus 410 using a plurality of antennaelements used in MIMO communication or diversity communication, isplaced on the upper part of portable radio device 400A.

Antenna apparatus 410 is provided with first antenna elements 111, 112and 113 for the first polarization direction, second antenna elements121 and 122 that are set in the direction orthogonal to the firstpolarization direction, switches 131, 132, 133 and 134 (not shown inFIG. 15A) that are set in one end of first antenna elements 111, 112 and113 and that switch the connections between first antenna elements 111,112 and 113 and second antenna elements 121 and 122, and feedingsections 141, 142 and 143 (not shown in FIG. 15A) that are provided infirst antenna elements 111, 112 and 113, respectively.

Antenna apparatus 410 differs from FIG. 8 only in arranging secondantenna elements 121 and 122 and switches 131, 132 and 133 on the sideopposite to the side of feeding sections 141, 142 and 143 of antennaelements 111, 112 and 113.

Also, as shown in FIG. 9B, it is possible to arrange antenna apparatus410 in the upper part of portable radio device 400A and further coverantenna apparatus 410 with cover 420.

The operations of antenna apparatus 410 configured as above are the sameas in Embodiment 1 and explanation will be omitted.

Thus, according to the present embodiment, similar to Embodiment 3, byswitching between switches 131 to 134 (SW 1 to SW 4), it is possible toacquire the antenna characteristics of various combinations. By thismeans, even in the case where mismatch of polarization occurs in areceiving antenna due to the antenna configuration of the base station,the rotation of propagating polarization and the gradient of theterminal (e.g. portable radio device 400), it is possible to improve thereceiving level by various variations of antenna polarizations. Inparticular, these antenna polarizations are effective to improve thereceived signal level in MIMO and diversity communication. Also, withthe present embodiment, similar to Embodiment 3, by switching betweenswitches 131 to 134 (SW 1 to SW 4) and changing operating antennaelements, it is possible to switch polarization characteristics withmore variations than in Embodiments 1 and 2, so that it is possible toprovide antenna performance to cope with the condition of polarizationthat changes every minute between a base station and a terminal. As aresult, it is possible to improve transmission capacity in variouspolarization environments and usage types.

(Embodiment 5)

FIG. 16 shows a perspective view of an outline configuration of aportable radio device mounting an antenna apparatus using a plurality ofantenna elements, according to Embodiment 5 of the present invention. Inthe explanation of the present embodiment, the same components as inFIG. 1 and FIG. 9A will be assigned the same reference numerals andoverlapping explanation will be omitted.

In FIG. 16, antenna apparatus 310 using a plurality of antenna elementsused in MIMO communication or diversity communication, is placed on theupper part of portable radio device 500A.

Also, switch controller 501 that controls switching between switches131, 132, 133 and 134 (not shown) of antenna apparatus 310, switchcontroller command section 502 that controls switch controller 501 andcommunication capacity calculating section 503 that calculates thecommunication capacity, are provided in portable radio device 500A.

Above switch controller command section 502 and communication capacitycalculating section 503 may be comprised of, for example,microprocessors or electronic circuits such as a logical circuit andtimer. Here, in the case of forming these sections with microprocessors,it is equally possible to use resources such as a CPU provided as a mainunit function in portable radio device 500A.

The operations of portable radio device 500A having antenna apparatus310 configured as above will be explained. The operations of antennaapparatus 310 are the same as in Embodiment 1 and explanation will beomitted, and the specific operations of the present embodiment will bedescribed.

Switch controller command section 502 sequentially switches betweenswitches 131, 132, 133 and 134 via switch controller 501, according topredetermined operation modes. For example, switch controller commandsection 502 commands switch controller 501 to switch between switches131, 132, 133 and 134 in a switching configuration to implement Mode 1,Mode 2 to Mode 3 in order, as shown in FIGS. 10A to 10C and FIG. 11. Bythis means, switches 131, 132, 133 and 134 are switched in a switchingconfiguration to implement above Mode 1, Mode 2 to Mode 3 in order.

Communication capacity calculating section 503 detects the communicationcapacities upon switching a switching configuration to implement Mode 1,Mode 2 to Mode 3 in order. Further, communication capacity calculatingsection 503 compares the communication capacities of those modes, andoutputs a signal to report the mode in which the highest communicationcapacity is found, to switch controller command section 502. Switchcontroller command section 502 gives a command to switch the switchconfiguration to the switch configuration corresponding to the mode inwhich the highest communication capacity is found. By this means,portable radio device 500A is operated so as to perform communication inthe mode in which the highest communication capacity is found.

The above operation flow is implemented at arbitrary timings. Also, itis equally possible to implement the operation flow at regular timeintervals.

Thus, according to the present embodiment, by switching between switches131 to 134 (SW 1 to SW 4) to perform communication in a mode in whichthe highest communication capacity is found, even in the case wheremismatch of polarization occurs in a receiving antenna due to theantenna configuration of the base station, the rotation of propagatingpolarization and the gradient of the terminal (e.g. portable radiodevice 300), portable radio device 500A can switch the polarizationcharacteristics with the best reception signal level and provide antennaperformance to cope with the condition of polarization that changesevery minute between the base station and a terminal. As a result, it ispossible to further improve transmission capacity in variouspolarization environments and usage types.

Also, by forming switch controller command section 502 and communicationcapacity calculating section 503 using resources such as a CPU providedas a main unit function in portable radio device 500A, it is possible toprovide an advantage of requiring no additional components and realizingthe configuration in an easy manner. Also, there is an advantage ofmaking it possible to set and change a specification in an easy manner.

Also, it is natural that the present embodiment can be combined withabove Embodiments 1 to 4.

The above explanation is an example of the best mode for carrying outthe present invention, and the scope of the present invention is notlimited to this.

The present invention is applicable to any apparatuses as long as theseapparatuses are equivalent to a communication apparatus having anantenna apparatus using a plurality of antenna elements for performingdiversity operations, MIMO communication or adaptive array antennaoperations. For example, the present invention is applicable to a mobiletelephone device and PHS (Personal Handy-phone System) as well asportable information terminals such as PDA (Personal Digital Assistant)and information processing apparatuses such as a laptop computer.

Also, in the above embodiments, a used frequency band is not limited tothe DTV band, and any bands are applicable. As a portable radio devicesupporting a plurality of frequency bands, in Japan, portable radiodevices are commercialized which use both PDC (Personal DigitalCellular) using a 900 MHz band and CDMA (Code Division Multiple Access)using a 2 GHz band. Even in foreign countries, portable radio devicesare commercialized which use GSM (Global System for Mobilecommunications) using a 900 MHz band, DCS (Digital Communication System)using a 1.8 GHz band, PCS (Personal Communication Services) using 1.9GHz and UMTS (Universal Mobile Telecommunication System) using a 2 GHzband. For example, a case is possible where the first frequency band isa 2 GHz single band and a second frequency band is comprised of threebands of 900 MHz band, 1.8 GHz band and 1.9 GHz band.

Also, although the name “portable radio device” is used for ease ofexplanation in the above embodiments, for example, “portable telephonedevice” and “wireless communication apparatus” are equally applicable.Also, a communication apparatus having an antenna apparatus may be abase station apparatus on the transmitting side, for example.

Also, the type, the number and the method of connecting circuits formingthe above portable radio device are not limited to the aboveembodiments.

Industrial Applicability

With the antenna apparatus and communication apparatus of the presentinvention, it is possible to provide a communication apparatus having anantenna apparatus using a plurality of antenna elements for performingdiversity operations, MIMO communication or adaptive array antennaoperations. Further, it is possible to provide optimal antennaperformance for received signals that attenuate or fluctuate due to thecondition of polarization that changes every minute between a basestation and a terminal. Especially, the present invention is useful fortechniques having an advantage of preventing the decrease incommunication capacity in communication using a plurality of antennaelements for performing diversity operations, MIMO communication oradaptive array antenna operations.

1. An antenna apparatus comprising: at least two first antenna elementsfor a first polarization direction; a second antenna element that is setin a direction orthogonal to the first polarization direction; a switchthat switches connections between the first antenna elements and thesecond antenna element; and a feeding section that is set in each of thefirst antenna elements.
 2. The antenna apparatus according to claim 1,wherein the switch switches the connections depending on a polarizationdirection.
 3. The antenna apparatus according to claim 1, wherein, whena number of feeding points of the feeding section is N (where N is anarbitrary natural number), a number of the first antenna elements andsecond antenna elements is N+(N−1), and a number of switches is (N−1)×2.4. A communication apparatus having an antenna apparatus used for MIMO(Multiple Input Multiple Output) or diversity, wherein the antennaapparatus is the antenna apparatus according to claim 1.